1. Field of the Invention
Aspects of this invention relate to a tubing seal, and in particular to a method and arrangement for producing a seal between two tubing sections. Other aspects of the invention relate to a tubing anchor, and to a method and arrangement for anchoring one tubing section relative to another. The different aspects of the invention have particular utility in downhole applications.
2. Description of the Related Art
In many instances it is desired to provide a seal between two overlapping tubing sections in a downhole environment. Where space permits, the seals may be formed of elastomeric packer elements or perhaps as metal-to-metal seals which are energised by spring packs or the like. However, in many applications there will not be sufficient space to accommodate such a sealing arrangement, for example in thin-wall tubing, and in such cases the seals are more often provided in the form of O-ring or chevron sealing members. It has also been proposed to create seals around expandable tubing using sealing members in the form of bands of relatively soft metal, as described in PCT/GB99/04365. In such cases, in order to create an effective seal, it is necessary for the sealing member to extend beyond the surface of the tubing. This makes the seal vulnerable to damage and dislodgement as the tubing is run into the bore.
It is among the objectives of aspects of the present invention to provide a method of forming a seal which obviates or mitigates these and other disadvantages of the prior art.
In other instances it is desired to anchor or secure one tubing section or tool relative to another. This is often achieved by means of slips, typically fingers or keys having a serrated or grooved outer face which co-operate with wedges or cams to push the slips radially outwards to engage with surrounding casing. However, such slips, and the associated slip energising or setting arrangement, occupy a relatively large volume. As described in applicant's International (PCT) Application No. PCT/GB9904365, it has been proposed to overcome this difficulty in some situations by providing a hanger arrangement in which inner tubing carrying small hard elements on its outer surface is expanded into engagement with surrounding tubing. However, the gripping elements are exposed to damage as the inner tubing is run into the bore and may, for example, be scraped from the tubing by contact with a ledge or other restriction. Also, the relatively hard elements may score or scrape the relatively soft material of the existing casing, or bore restrictions such as valve seats, as the tubing is run in.
It is among the objects of other aspects of the invention to provide an anchoring arrangement which obviates or mitigates these disadvantages.